Adoption

Each edition of the NEC is enforced by authorities only after it is individually adopted by state or local governments in the USA. Figure 1 shows the status of adoption as of November 1, 2020.⁴ The NFPA updates this information on its website at https://www.nfpa.org/NEC/NEC-adoption-and-use/NEC-adoption-maps. As of November 2020, at least four different editions of the NEC were simultaneously enforced in the USA.

KEY 2020 CHANGES FOR BACKUP POWER

While changes across the NEC are wide-ranging, select changes that impact backup power systems are summarized in the following sections.

Reconditioned Equipment

The NEC has clarified and added language regarding the use of reconditioned power equipment. Article 110.3(A)(3)reads:⁵

In judging equipment, considerations such as the following shall be evaluated:
Suitability for installation and use in conformity with this Code
Informational Note No. 1: Equipment may be new, reconditioned, refurbished, or remanufactured.

To clarify the requirement, a definition was added to Article 100 of the Code. “Reconditioned” is defined as “Electromechanical systems, equipment, apparatus, or components that are restored to operating conditions. This process differs from normal servicing of equipment that remains within a facility, or replacement of listed equipment on a one-to-one basis.⁶ An informational note clarifies that the term “is frequently referred to as rebuilt, refurbished, or remanufactured.”

In Article 110.21(A)(2), corresponding wording requires that reconditioned equipment be identified accordingly, the original listing mark be removed, and that the equipment be marked with “the name, trademark, or other descriptive marking by which the organization responsible for reconditioning the electrical equipment can be identified, along with the date of the reconditioning.”⁷ Refer to the standard for exceptions for certain industrial facilities.

The scope of reconditioning is defined in Article 408 of the code, which states that the reconditioning process shall (1) use “design qualified parts” verified under applicable standards, and (2) be performed in accordance with manufacturer’s instructions, if any. This article also requires that fire, water, and smoke-damaged equipment be evaluated by the manufacturer or a qualified laboratory before return to service. Article 408.8 permits reconditioning of switchboards and switchgear, but limits reconditioning of panel boards to replacement of their interior assemblies.⁸ Elsewhere, Article 700.⁵(C) - Automatic Transfer Switches prohibits reconditioning of Automatic Transfer Switches, which is also repeated in Articles 701, 702, and 708 of the standard.

For additional reference, the National Electrical Manufacturers Association provides further guidance on types of equipment that may or may not be suitable for reconditioning. Further details are available in its document entitled NEMA Technical Position on Reconditioned Equipment.⁹

Protection for Energized Parts

The 2020 NEC introduced two requirements to reduce the risk of people and objects from inadvertently contacting energized parts. For service equipment, Article230.62(C) states, “Barriers shall be placed in service equipment such that no uninsulated, ungrounded service bus bar or service terminal is exposed to inadvertent contact by persons or maintenance equipment while servicing load terminations.”¹⁰ This requirement was relocated from Article 408 - Switchboards, Switchgear, and Panelboards in the 2017 NEC. Its inclusion in Article 230 – Services of the 2020 NEC makes it applicable to all service entrance equipment.

For switchboards, Article 408.13(C)(3) specifies the arrangement of ungrounded conductive terminals as follows:

In judging equipment, considerations such as the following shall be evaluated:
Suitability for installation and use in conformity with this Code
Informational Note No. 1: Equipment may be new, reconditioned, refurbished, or remanufactured.

While these provisions are new to the NEC, they respectively reflect guidance already presented in UL 67 – Panelboards and UL 891–Standard for Switchboards.

Arc Flash Mitigation

The potential for arc flashes to occur in power equipment is a serious safety topic, which is why the NEC requires clearing time reduction measures on circuit breakers rated 1200 Amps or more. Article 240.87(B) of the 2017 NEC requires one of the following means:¹¹

    1. Zone-selective interlocking
    2. Differential relaying
    3. Energy-reducing maintenance switching with local status indicator
    4. Energy-reducing active arc flash mitigation system
    5. An instantaneous trip setting that is less than the available arcing current
    6. An instantaneous override that is less than the available arcing current
    7. An approved equivalent means

Potential issues with this wording include that (1) it could be read that temporary adjustment of an instantaneous trip setting is sufficient, and (2) only options 5 and 6 must limit the arcing current. The 2020 NEC clarifies this article as follows, where the underlined words show added text:

One of the following means shall be provided and shall be set to operate at less than the available arcing current:¹²

(1) Zone-selective interlocking
(2) Differential relaying
(3) Energy-reducing maintenance switching with local status indicator
(4) Energy-reducing active arc flash mitigation system
(5) An instantaneous trip setting. Temporary adjustment of the instantaneous trip setting to achieve arc energy reduction shall not be permitted.
(6) An instantaneous override
(7) An approved equivalent means


The new language makes clear that whatever means employed must operate at less than the available arcing current. The 2020 Edition also added Article 240.87(C) - Performance Testing, which requires (1) documents showing that the implemented arc energy reduction measures operate below the arcing current, and (2) documented field tests that prove the installed measure performs as intended.

Transfer Equipment for Emergency Systems

Article 700.5(A) specifies general conditions regarding acceptable transfer devices. Changes to this requirement include:
1.The 2017 Edition required that the transfer equipment be identified for emergency use. The 2020 Edition states more specifically that the equipment shall be marked for emergency use.
2.The 2020 Edition requires that transfer switches be listed (by a ratings agency – for example, Underwriters Laboratories).
3.The 2020 Edition adds a prohibition against meter-mounted transfer switches for emergency use.


Bypass-Isolation Transfer Switches for COPS Facilities

Article 708 of the NEC sets forth requirements for Critical Operations Power Systems (COPS). These provide power to systems and facilities engaged in public safety or national security. In the 2017 NEC, Article 708 permits the use of a bypass-isolation switch. Figure 2 illustrates an example. (For an interactive visualization, visit www.ascopower.com.)

The 2020 version of the NEC now requires the use of a bypass-isolation switch for facilities where COPS loads are fed through a single transfer switch. The 2020 NEC adds Article 708.24(D), which reads:¹³

Where loads are supplied by only one automatic transfer switch, the automatic transfer switch shall include a bypass isolation switch to facilitate maintenance as required in 708.6(C) without jeopardizing continuity of power. When the bypass isolation transfer switch is in the bypass mode, either it shall automatically initiate transfer between power sources upon loss of the connected power source or it shall remain actively supervised by a qualified person who can manually initiate a transfer between power sources.

To comply with the new requirement, facilities must use an automatic transfer switch that includes a bypass-isolation switch that transfers load automatically, or have someone qualified to operate the transfer switch manually

SUMMARY

The 2020 NEC introduced new requirements, some of which impact the design and/or operation of backup power systems and equipment. The select changes described in this document are summarized in Table 2.

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¹ NFPA 70 - National Electrical Code, 2020 Edition, National Fire Protection Agency, 2019. https://nec2020.nfpa.org/code/eb61ef8f-b559-487b-8499- 9f0b11e56c6d/b3facf69-215c-418b-9ea4-27760f5f6040/, ^{accessed November 10, 2020.
2} Free online access to the NEC® and other electrical standards, National Fire Protection Agency.https://www.nfpa.org/NEC/About-the-NEC/Free-onlineaccess-to-the-NEC-and-other-electrical-standards, accessed November 11, 2020.
³ National Electrical Code Requirements for Emergency Power Transfer Switching, ASCO Power Technologies, Inc., 2019. https://www.ascopower.com/ us/en/download/document/TS-WP-NECREQ/, accessed November 11, 2020.
⁴ NEC Enforcement Map, National Fire Protection Agency, November 1, 2020. https://www.nfpa.org/NEC/NEC-adoption-and-use/NEC-adoption-maps, accessed November 10, 2020.
⁵ NFPA 70 - National Electrical Code, 2020 Edition, National Fire Protection Agency, 2019. Article 110.3-Examination, Identification, Installation, Use, and Listing (Product Certification) of Equipment. https://nec2020.nfpa.org/code/eb61ef8f-b559-487b-8499-9f0b11e56c6d/e075695c-442f-42a9-8ae0- 406e5f796801/, accessed November 10, 2020.
⁶ Ibid. Article 100 - Definitions
⁷ Ibid. Article 110.21 - Marking
⁸ Ibid Article 408, et seq. - Switchboards, Switchgear, and Panelboards
⁹ NEMA CS 100-2020 - NEMA Technical Position on Reconditioned Equipment, National Electrical Manufacturers Association, 2020. https://www.nema. org/standards/view/nema-technical-position-on-reconditioned-equipment, accessed November 10, 2020.
¹⁰ NFPA 70 - National Electrical Code, 2020 Edition - National Fire Protection Agency, 2019. Article 230.62 – Service Equipment – Closed or Guarded. https://nec2020.nfpa.org/code/eb61ef8f-b559-487b-8499-9f0b11e56c6d/463bba44-7758-420d-9060-6c7e40d0fd5a/8d5a6e98-0e30-487e-8747- 46b9e5b67cae/, accessed November 10, 2020.
¹¹ NFPA 70 - National Electrical Code, 2017 Edition, National Fire Protection Agency, 2016. Article 240.87 - Arc Energy Reduction.
¹² NFPA 70 - National Electrical Code, 2020 Edition. National Fire Protection Agency, 2019. Article 240.87 - Arc Energy Reduction. https://nec2020.nfpa. org/code/eb61ef8f-b559-487b-8499-9f0b11e56c6d/463bba44-7758-420d-9060-6c7e40d0fd5a/2380114f-8f40-44d8-85cb-eccb45b601e1/, accessed November 10, 2020.
¹³ Ibid. Article 708.24 –Transfer Equipment

● https://www.nfpa.org/NEC/NEC-adoption-and-use/NEC-adoption-maps - https://www.nfpa.org/NEC/NEC-adoption-and-use/NEC-adoption-maps
● www.ascopower.com - https://www.ascopower.com/us/en/